Honda Fit: 86 mpg from the next hyper-efficient hybrid

Could your next car get 86 mpg? It might if it's a Honda. The next-generation Honda Fit subcompact will be unveiled this fall and arrive in the US in the first half of 2014. Most of the buzz over the new Fit, called the Honda Jazz in some countries) is the hybrid version, which promises a 35% improvement in fuel economy. The US currently gets the gasoline Honda Fit and EV Fit -- not the hybrid Fit -- but that could change with the next model.

Atkinson engine, 7-speed double clutch transmission, electric motor

Under the umbrella of Honda's Earth Dreams(Opens in a new window) Technology program, the new Fit Hybrid will be the first to employ Honda's Intelligent Dual Clutch Drive system, or i-DCD. The gasoline power comes from a 1.5-liter, four-cylinder Atkinson cycle engine. A single electric motor is packaged with a seven-speed dual clutch transmission, linked through an intelligent power unit (IPU) to a lithium-ion storage battery. An Atkinson engine has an effectively shorter compression stroke (when the piston moves upward) than the downward power stroke, accomplished by not immediately closing each cylinder's intake valve. It captures more of the power in the fuel-air mixture.

When starting out, the clutches disengage the gas engine and the Fit Hybrid starts off on battery power. The clutches engage the engine and gearbox under sporty (hard) acceleration and at higher speeds. When the Fit Hybrid decelerates, the gas engine is again disengaged.

Honda has claimed a 35% increase is compared to the current Fit Hybrid's integrated motor assist (IMA) configuration. The IMA electric motor only runs when the gasoline engine runs, functioning much like a turbocharger. This is called a mild hybrid or weak hybrid configuration. A hybrid such as the Prius that can run on battery power alone is a strong hybrid, and who wouldn't prefer strong over mild, let alone weak?

IMA may be cost-effective tech, but lots of hybrid owners want to see -- and show their friends -- a car that runs on battery alone for a mile or two. This is what happens when you let engineers have input into how a company runs: They pick solutions that make cost-effective sense. Sometimes the market agrees, other times not. Honda has long argued nobody needs an engine of more than six cylinders and it turns out they're right, but that hurt the Acura brand competing against V8 offerings from Lexus, Audi, BMW and Mercedes-Benz the last two decades. Honda has also been one or two gears shy of the competition in transmissions, arguing that four or five forward gears was  fine -- "look at our mpg figures, not the numbers of gears." Now, they too are creeping upwards to as many as seven (the industry record is currently nine). The IMA hybrid is giving way to the i-DCD hybrid. At the very least, IMA served its purpose and Honda is moving on to a more efficient technology.

Next page: Flavors of Honda hybrids

Three hybrid flavors from Honda

Honda will actually have three hybrid configurations going forward with one, two, and three electric motors for small, medium, and large/sporty cars. All will use lithium-ion batteries. The previous IMA hybrids used nickel-metal hydride.

The one-motor (electric motor) Intelligent Dual Clutch Drive design is what's on the new Fit hybrid and likely other small Hondas. The dual-clutch system is an automated mechanical transmission, meaning there's a clutch (actually, two) as on manual gearboxes, but it's automated. The car, rather than the driver's left foot, activates the clutch. Many European cars use DCT transmissions and they've all but killed off the manual gearbox among performance cars.

The two-motor Intelligent Multi Mode Drive promises the highest efficiency, according to Honda researchers. It's suited for plug-in hybrids, the ones that can go 20-40 miles on batteries before switching over to the combustion engine. It will be on the 2014 Honda Accord plug-in hybrid electric vehicle (PHEV). If there's enough battery power, this drivetrain offers three modes. EV Mode is battery-only; it regains some of the expended energy braking and going down hills. Engine Drive is for medium and high-speed driving; the hybrid stuff is along for the ride here, with the gasoline engine directly connected by a lock-up clutch to the drive wheels. Hybrid Drive is a combination for city driving and also for extra power accelerating on the highway, where the electric motor adds boost just as a turbocharger does.

The three-motor Super-Hybrid All-Wheel-Drive mode (SH-AWD) is for performance Hondas and Acuras. It uses a V6 gas engine, has the performance of a V8, and the fuel economy of a four-cylinder, Honda says. A 3.5-liter V6 engine is up front, along with the seven-speed DCT and an electric motor to drive the front wheels. Two more electric motors in back provide power for the left and right rear wheels and torque distribution. There is no driveshaft sending mechanical power to the rear wheels, which saves space and weight. Acura's existing SH-AWD gas-engine cars have the ability to overpower the outside wheel going around corners or on slippery patches. Depending on what kind of driver you are, SH-AWD provides an added measure of safety or performance.